COSTAR GROUP, INC. — Director's Dealing 2010

Jun 1, 2010

SEC Form 4 — Statement of Changes in Beneficial Ownership

Issuer: COSTAR GROUP INC (CSGP)
CIK: 0001057352
Period of Report: 2010-05-28

Reporting Person: Radecki Brian J (Chief Financial Officer)

Non-Derivative Transactions

Date	Security	Code	Shares	Price	A/D	Holdings After	Ownership
2010-05-28	Common Stock, par value $0.01 per share	F	66	$40.77	Disposed	32467	Direct

Footnotes

F1: Represents all shares of Common Stock owned, consisting of 7,858 shares of Common Stock and 24,204 shares of Common Stock subject to unvested Restricted Stock Grants. The shares of Common Stock owned and set out in this line item include a total of 1,252 shares purchased to date by the reporting person pursuant to bi-weekly purchases made under the Company's Employee Stock Purchase Plan.